Closed loop load force estimation systems and methods

ABSTRACT

What is described is a system for determining a force applied to an outer disc of an aircraft brake by an actuator motor. The system includes a current sensor coupled to the actuator motor and configured to detect a detected amount of current applied to the actuator motor. The system also includes a controller coupled to the current sensor. The controller is configured to determine an estimated current. The controller is also configured to receive the detected amount of current. The controller is also configured to determine an adjusted current based on the detected amount of current and the estimated current. The controller is also configured to determine an estimate of the force applied to the outer disc based on the adjusted current.

FIELD

The present disclosure relates to aircraft brakes, and moreparticularly, to a system for determining a braking force applied to anouter disc of an aircraft brake.

BACKGROUND

Aircraft brakes include alternating stators and rotating discs thatrotate about an axis. Wheels of the aircraft are coupled to the rotatingdiscs. The stators and rotating discs are axially enclosed by two outerdiscs. In order to cause the rotating discs to slow down or stoprotating (i.e., brake), force is applied to at least one of the outerdiscs, forcing the outer discs, the stators and the rotating discstogether. When forced together, friction reduces the angular speed ofthe rotating discs.

A motor converts electrical energy into mechanical energy that causesthe force to be applied to the outer disc using an actuator. It isdesirable to determine the amount of force applied to the outer disc. Anactuator may include a force sensor to determine this amount of force.

SUMMARY

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, the following descriptionand drawings are intended to be exemplary in nature and non-limiting.

In accordance with various embodiments, a system for determining a forceapplied to an outer disc of an aircraft brake by an actuator isdisclosed. The system includes a current sensor coupled to the actuatorand configured to detect a detected amount of current applied to theactuator. The system also includes a controller coupled to the currentsensor. The controller is configured to determine an estimated current.The controller is also configured to receive the detected amount ofcurrent. The controller is also configured to determine an adjustedcurrent based on the detected amount of current and the estimatedcurrent. The controller is also configured to determine an estimate ofthe force applied to the outer disc based on the adjusted current.

Also disclosed is an exemplary method for determining a force applied toan outer disc of an aircraft brake by an actuator. The method includesdetecting, by a current sensor, a detected amount of current. The methodalso includes determining, by a controller, an estimated current. Themethod also includes receiving, by the controller, the detected amountof current. The method also includes determining, by the controller, anadjusted current based on the detected amount of current and theestimated current. The method also includes determining, by thecontroller, an estimate of the force applied to the outer disc based onthe adjusted current.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the drawing figures, wherein like numeralsdenote like elements.

FIG. 1 illustrates an aircraft brake, in accordance with variousembodiments;

FIG. 2 illustrates a block diagram of an aircraft electromechanicalbrake actuator control system, in accordance with various embodiments;

FIG. 3A illustrates input parameters to a force observer module, inaccordance with various embodiments;

FIG. 3B illustrates a system for determining a constant K-nominal, inaccordance with various embodiments;

FIG. 3C illustrates logic for determining a mode of operation of anactuator, in accordance with various embodiments;

FIG. 3D illustrates a system for determining a variable ForceMaxLimit,in accordance with various embodiments;

FIG. 3E illustrates a system that is used to calculate an estimatedforce, in accordance with various embodiments;

FIG. 4 illustrates a closed-loop system for estimating a force appliedby an actuator, in accordance with various embodiments;

FIG. 5A illustrates a plot that represents a measured value of forceapplied by an actuator as a current is applied to the actuator and aplot that represents the estimated value of the force using the systemof FIG. 3E, in accordance with various embodiments;

FIG. 5B illustrates another plot that represents a measured value offorce applied by an actuator as a different current is applied to theactuator than in FIG. 5A and another plot that represents the estimatedvalue of the force using the system of FIG. 3E, in accordance withvarious embodiments; and

FIG. 5C illustrates a plot that represents an estimated amount ofcurrent over a period of time using an open loop system and anotherestimated amount of current over the period of time using theclosed-loop system of FIG. 4.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration and their best mode. While these exemplary embodiments aredescribed in sufficient detail to enable those skilled in the art topractice the disclosure, it should be understood that other embodimentsmay be realized and that logical, chemical, and mechanical changes maybe made without departing from the spirit and scope of the disclosure.Thus, the detailed description herein is presented for purposes ofillustration only and not of limitation. For example, the steps recitedin any of the method or process descriptions may be executed in anyorder and are not necessarily limited to the order presented.Furthermore, any reference to singular includes plural embodiments, andany reference to more than one component or step may include a singularembodiment or step. Also, any reference to attached, fixed, connected orthe like may include permanent, removable, temporary, partial, fulland/or any other possible attachment option. Additionally, any referenceto without contact (or similar phrases) may also include reduced contactor minimal contact.

FIG. 1 illustrates an aircraft brake 100 in accordance with variousembodiments. Aircraft brake 100 includes a plurality of actuator motors102A, 102B, a plurality of electromechanical brake actuators 104A, 104B,a plurality of ball nuts 106A, 106B, a plurality of pucks 108A, 108B, anouter disc 111 and an outer disc 110, and a plurality of rotating discs112A, 112B, 112C, 112D and stators 114A, 114B, 114C positioned in analternating fashion between outer disc 111 and outer disc 110. Rotatingdiscs 112A, 112B, 112C, 112D may rotate about an axis 115 and thestators 114A, 114B, 114C may have no angular movement relative to axis115. Wheels may be coupled to rotating discs 112A, 112B, 112C, 112D suchthat a linear speed of the aircraft is proportional to the angular speedof rotating discs 112A, 112B, 112C, 112D. As force is applied to outerdisc 110 towards outer disc 111 along the axis of rotation 115, rotatingdiscs 112 and stators 114 are forced together in an axial direction.This causes the rotational speed of rotating discs 112A, 112B, 112C,112D to become reduced (i.e., causes braking effect) due to frictionbetween rotating discs 112A, 112B, 112C, 112D, stators 114A, 114B, 114C,outer disc 111 and outer disc 110. When sufficient force is exerted onrotating discs 112 via outer disc 110, the rotating discs 112A, 112B,112C, 112D will stop rotating.

In order to exert this force onto outer disc 110, actuator motor 102Amay cause electromechanical brake actuator 104A to actuate. Actuatormotor 102A may be a brushless motor, such as a permanent magnetsynchronous motor (PMSM), a permanent-magnet motor (PMM) or the like.When electromechanical brake actuator 104A actuates, it causes ball nut106A to extend towards outer disc 110, thus applying force on outer disc110 towards outer disc 111. Puck 108A is positioned between ball nut106A and outer disc 110. Puck 108A may be constructed of a softer and/ormore compliant material than ball nut 106A such that when ball nut 106Ais forced towards outer disc 110, puck 108A prevents outer disc 110 frombecoming damaged.

Electromechanical brake actuator 104A is actuated in response to currentbeing applied to actuator motor 102A. The amount of force applied byelectromechanical brake actuator 104A is related to the amount ofcurrent applied to actuator motor 102A. It is desirable to determinethis amount of force. One way to determine this force is to use a forcesensor within electromechanical brake actuator 104A. However, it may bedesirable to determine this force without the use of a force sensor.

Aircraft brake 100 may include a current sensor (such as current sensor208 of FIG. 2) to detect an amount of current provided to actuator motor102A. Because the amount of force applied by electromechanical brakeactuator 104A is related to the current applied to actuator motor 102A,it is possible to estimate the force using the detected amount ofcurrent. Thus, a controller or controller may receive the detectedcurrent and estimate a force based on the detected current.

FIG. 2 illustrates a block diagram of an aircraft electromechanicalbrake actuator control system in accordance with various embodiments.Block 205 includes mechanical components. The other blocks may beimplemented on one or more controllers and/or controllers. For example,the blocks other than block 205 may be stored in a non-transitorystorage medium and performed by a controller and/or controller, may bestored in a special-use controller, may be implemented in a fieldprogrammable gate array (FPGA), or the like. Block 205 includes acurrent sensor 208 coupled to an actuator motor 206 (similar to or thesame as actuator motor 102A). Current sensor 208 is configured to detectan amount of current supplied to actuator motor 206. A resolver 214 isalso coupled to actuator motor 206. Resolver 214 measures the rotationalposition and speed of actuator motor 206. Actuator motor 206 is alsocoupled to a gear transmission 210 and a ball screw 212.

A force observer module 216 is coupled to block 205. Force observermodule 216 is configured to estimate the force of actuator 104A based ondata from current sensor 208 and/or resolver 214. Force observer module216 may be a controller and/or controller or may be implemented in acontroller and/or controller.

In block 217, the estimated force is compared with a force commandsignal. The output of block 217 is provided to a force position controlmodule 200. Output from force position control module 200 is summed withthe rotational speed of actuator motor 206 in block 201. The result ofthe summation in block 201 is provided to a velocity control module 202.The output from velocity control module 202 is summed with the detectedcurrent from current sensor 208 in block 203. The output from block 203is provided to a current control module 204. The output of currentcontrol module 204 is provided to actuator motor 206 as a controlsignal.

FIGS. 3A through 4 illustrate logic within force observer module 216 inaccordance with various embodiments. The logic may be implemented inhardware and/or software. In various embodiments, the logic may bestored as machine-readable instructions on a non-transitory memory andperformed by a controller. In various embodiments, the logic may bestored on a special-use controller or a field programmable gate array.

FIG. 3A illustrates input parameters 390 to force observer module 216.Input parameters 390 may be known parameters for the given motor andthus be predetermined. Input parameters 390 include a max force 300,which may be measured in pound force (lbf), newtons, or the like. Maxforce 300 represents the maximum force that can be applied by actuator205. Another input is a max current 302, which may be measured in amps.Max current 302 represents the amount of current to be applied toactuator motor 206 to cause actuator 205 to apply the maximum amount offorce. Another input is an efficiency fraction 304. Efficiency fraction304 indicates the efficiency of the actuator. In the example illustratedin FIG. 3A, max force 300 is given to be 7,857 pounds, max current 302is given to be 6.5 amps and efficiency fraction 304 is given to be 0.65.

FIG. 3B illustrates a system 391 for determining a constant K-nominal306. K-nominal indicates a relationship between applied force andapplied current for actuator motor 206, such that a current may bemultiplied by K-nominal 306 to determine a force and a force can bedivided by K-nominal 306 to determine a current. System 391 utilizes maxforce 300 and max current 302 as inputs. In block 305, the max force 300is divided by the max current 302, resulting in K-nominal 306.

FIG. 3B also illustrates a system 392 for determining a mode of actuator205 of FIG. 2. With brief reference to FIG. 5A, two plots are shownillustrating the relationship of force and current as current is appliedto actuator 205 in accordance with various embodiments. Plot 500illustrates the estimated force using the methods described herein andplot 502 illustrates the measured force. As illustrated, plot 500includes a first part 504 corresponding to a first mode, a second part506 corresponding to a second mode and a third part 508 corresponding toa third mode. In the first mode, the amount of current applied toactuator motor 206 is increasing and the force is increasingsubstantially proportionally. In the second mode, the amount of currentapplied to actuator motor 206 is decreasing a first amount. However, theforce does not decrease significantly. This is a result of “stiction”(e.g., static friction) in actuator 205. In the third mode, once the“stiction” is overcome, the force is reduced substantiallyproportionally to the current as the current decreases a second amount.

Returning to FIG. 3B, system 392 is designed to determine in which modeactuator 205 is operating. The system 392 utilizes input current 308 asan input. Input current 308 may be provided to system 392. Input current308 is applied to calculate mode of operation block 310, which generatesmode 312 as an output. Mode 312 indicates the mode in which actuator 205is operating.

FIG. 3C illustrates the logic within calculate mode of operation block310. As illustrated, input current 308 is utilized as an input. Thefirst portion of the calculate mode of operation block 310 is tocalculate a filtered derivative of the current, or iDot 326. iDot 326represents the estimated time rate of change that occurs in thederivative of current. Blocks 316, 318, 324, 322, 320 and 328 representa low pass filtered differentiator used to calculate iDot 326. Block 320is a simulation artifact and may not exist in various implementations.

iDot 326 is then compared to zero in block 330, block 332 and block 334.If iDot 326 is greater than 0, then block 330 will output a 1, otherwiseblock 330 will output a 0. This 1 output corresponds to the first mode,indicating that the current is increasing and the force will increaseproportionally to the current. If iDot 326 is equal to 0, then block 332will output a 2. Otherwise, block 332 will output 0. This 2 outputcorresponds to the second mode, indicating that the force will not begreatly reduced as the current decreases. If iDot 326 is less than 0,then block 334 will output a 3. Otherwise, block 334 will output 0. The3 output corresponds to the third mode, indicating that the force willbe reduced substantially proportionately to the current as the currentis reduced.

Block 336 receives the input from block 330, block 332 and block 334 andadds them together. The resulting sum indicates the mode 312. If themode is equal to 1, then actuator 205 is in the first mode. If the modeis equal to 2, then actuator 205 is operating in the second mode. If themode is equal to 3, then actuator 205 is operating in the third mode.

FIG. 3D illustrates a system 393 for determining a variableForceMaxLimit 350, indicating the maximum force applied during the mostrecent iteration of the first mode. ForceMaxLimit 350 will be used inthe force estimation during the second mode. The input to system 393 ismode 312. In block 338, in response to the current beginning todecrease, a true signal will be generated. The true signal generatedfrom block 338 will cause a sample and hold block 346 to become active.Sample and hold block 346 also receives a force previous value (ForcePV342) signal. ForcePV 342 represents an estimated force that has beendelayed. A unit delay block 367 in a system 395 of FIG. 3E receives theestimated force and provides the estimated force as ForcePV 342 after apredetermined delay.

When block 338 outputs a true signal, sample and hold block 346 willstore and output ForcePV 342 until a new true signal is generated inblock 338. Sample and hold block 346 will generate the stored ForcePV342 as ForceMAXLimit 350. ForceMAXLimit 350 corresponds to the maximumestimated force during the first mode or the second mode.

FIG. 3D also illustrates a system 394 for calculating another variable,ForceMINLimit 352, indicating the minimum force applied during the mostrecent iteration of the third mode. ForceMINLimit 352 will be used inthe force estimation during the second mode. Mode 312 is an input tosystem 394. In block 340, a true signal is generated in response to thecurrent beginning to increase. Sample and hold block 348 also receivesForcePV 342. When the output from block 340 is true, ForcePV 342 will bestored in block 348, and block 348 will output the value asForceMINLimit 352 until a new “true” signal is generated in block 340.

FIG. 3E illustrates a system 395 that is used to calculate an estimatedforce 380. Estimated force 380 is the output of system 395.

Efficiency fraction 304 is a normalized value that ranges from 0 to 1. Avalue of one is ideal, meaning that actuator 205 is completely efficientand has no losses. With brief reference to FIG. 5A, the slope of firstpart 504 is equal to input current 308 multiplied by efficiency fraction304. The slope of third part 508 is equal to input current 308 dividedby efficiency fraction 304.

Returning to FIG. 3E, in block 354, input current 308 is multiplied byefficiency fraction 304. The output of block 354 represents therelationship of the current and force measurements during the firstmode. In block 376, input current 308 is divided by efficiency fraction304. The resulting value represents the relationship of the current andthe force during the third mode.

Block 356 represents a case statement to be used for a selection of arelationship of the current and the force based on the mode. The mode312 is provided as a selecting variable and the output of block 354 andblock 376 are provided as selectable inputs. During the first mode (whenmode=1), block 356 will output the output of block 354. During the thirdmode (when mode=3), block 356 will output the output of block 376.During the second mode (when mode=2), block 356 will output a valuecalculated elsewhere in system 395 (output of block 374).

In block 358, the output of block 356 is multiplied with K-nominal 306,the value calculated in system 391. When K-nominal is multiplied withthe output of block 356, the resulting signal indicates a force value.The value of force is stored as force1 360.

Block 368 will output a true signal if mode 312 is not equal to 1. Thelogic in block 368 is used to initialize system 395.

Block 370 will output a true signal if ForceMAXLimit 350 is greater than0. If block 370 and block 368 both output a true signal, then block 372will output a true signal.

Block 362 compares ForceMAXLimit 350 and force1 360 and outputs thesmaller of the two signal values. Block 364 compares force1 360 andForceMINLimit 352 and outputs the larger of the two signal values.

While the output of block 372 is true, block 366 will output the signalgenerated in block 362. When the output of block 372 is false, block 366will output the signal generated in block 364. The logic implemented inblock 368, 370, 372, 362, 364 and 366 generates the estimated force whenthe mode is equal to 2.

Block 378 is a limiter, which prevents the output of block 366 fromdropping below 0. The output of block 378 is estimated force 380.

The output of block 366 is driven through unit delay block 367, whichdelays the input signal (corresponding to the estimated force) by apredetermined period of time, such as one clock cycle, two clock cycles,1 millisecond, etc. The output of block 367 is ForcePV 342, the previousvalue of the estimated force. In block 374, ForcePV 342 is divided byK-nominal 306.

The output of block 356 is multiplied by K-nominal 306 to result in aforce value. Because ForcePV 342 is already a force value, it is dividedby K-nominal 306 prior to entering case block 356 so that it can beconverted back to a force value in block 358 via multiplication withK-nominal 306.

FIG. 4 illustrates a closed-loop system 401 for estimating force appliedby actuator 205. System 401 may be implemented in a machine-readablenon-transitory medium and performed by a controller. In variousembodiments, system 401 may be implemented on a special use controller,FPGA or the like. In various embodiments, system 401 may be implementedon more than one controller or controller.

System 401 outputs ForceCL 408 as the closed-loop estimate of the force.ForceCL 408 is the output of force observer module 216. System 401 mayalso output an estimated current, indicated as iHatCL 416. ForceCL 408and iHatCL 416 are determined based on input parameters 390 and Measuredcurrent 400. Measured current 400 represents the measured current, suchas by current sensor 208 of FIG. 2.

In module 402, the difference between the Measured current 400 andiHatCL 416 is calculated. Module 404 represents a PI controller, whichperforms an integration function based on the difference calculated inmodule 402. Module 404 outputs a current value which will force measuredcurrent 400 and iHatCL 416 to become close in value.

Module 406 represents a low pass filter. The low pass filter is used inorder to reduce noise on the current signal generated in module 404. Theoutput of module 406 is an adjusted current signal representing anadjusted current value.

The adjusted current signal generated by the low pass filter will beprovided to a current to force module 407. Current to force module 407is a module capable of determining a force value based on a currentvalue. For example, current to force module 407 may be system 395. Theadjusted current signal may be provided to system 395 as input current308. Current to force module 407 will then output an estimated force 380based on the adjusted current signal. The output of current to forcemodule 407 at this point in the closed-loop system may be output asForceCL 408, the estimated force of actuator 205.

ForceCL 408 is then input into a force to current algorithm 409. In FIG.4, a specific force to current algorithm 409 is illustrated. However,system 401 may operate with any algorithm that is capable of determiningan estimated current based on a force value. In particular, force tocurrent algorithm 409 converts ForceCL 408 into an estimated current,iHatCL 416.

In FIG. 4, force to current algorithm 409 includes block 414, module410, module 412 and current to force module 411. iHatCL 416 is providedto current to force module 411 as input current 308. Current to forcemodule 411 acts the same as current to force module 407, and may also beperformed by system 395. The output of current to force module 411 is atemporary estimated force. The temporary estimated force is thencompared with ForceCL 408 in block 414. Block 414 outputs a forcedifference which is the difference in the temporary estimated force andForceCL 408.

In module 410, the resulting difference of block 414 is amplified by0.05. In module 412, the result of module 410 is integrated. The resultof module 412 is the estimated current, iHatCL 416.

FIG. 5A illustrates plot 502 that represents a measured value of theforce applied by actuator 205 as a current is applied to actuator motor206 in accordance with various embodiments. Plot 500 represents theestimated value of the force using system 401. In FIG. 5A, up to 6.5amps is applied to the actuator motor 206. As illustrated, the estimatedforce is similar to the measured force.

FIG. 5B illustrates a plot 512 that represents the measured force when acurrent up to 3 amps is applied to actuator motor 206 in accordance withvarious embodiments. Plot 510 illustrates the estimated force usingsystem 401. As illustrated, the estimated force is similar to themeasured force during a first part 514 representing the first mode, asecond part 516 representing the second mode and a third part 518representing the third mode.

FIG. 5C illustrates a plot 520 of time and current that represents boththe actual current and the current estimated using system 401 inaccordance with various embodiments. FIG. 5C also includes a plot 522 oftime and current that illustrates the estimated current in a systemsimilar to system 401 that is open-loop (i.e., not including module 402and 404).

In FIG. 5C, the X axis represents time in seconds and the Y axisillustrates current in amps. The first segment 524 of FIG. 5 illustratesthe current increasing as time progresses. As illustrated, both plot 520and plot 522 represent similar estimated currents within first segment524. Likewise, in segment 526 while the current is remaining constant,both plot 520 and plot 522 illustrate that the estimated currents aresimilar.

In segment 528, the open-loop estimation of current (plot 522) remainsconstant while the actual current and the closed-loop estimation ofcurrent (plot 520) decrease. This illustrates that the closed-loopestimation of current is more accurate than the open-loop estimation ofcurrent. In segment 530, the open-loop estimation of current againmatches the actual current and the closed-loop estimation of current.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosure. The scope of the disclosure is accordinglyto be limited by nothing other than the appended claims, in whichreference to an element in the singular is not intended to mean “one andonly one” unless explicitly so stated, but rather “one or more.”Moreover, where a phrase similar to “at least one of A, B, or C” is usedin the claims, it is intended that the phrase be interpreted to meanthat A alone may be present in an embodiment, B alone may be present inan embodiment, C alone may be present in an embodiment, or that anycombination of the elements A, B and C may be present in a singleembodiment; for example, A and B, A and C, B and C, or A and B and C.Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment”, “an embodiment”,“various embodiments”, etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f) unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises”,“comprising”, or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

What is claimed is:
 1. A system for determining a force applied to adisc brake system of an aircraft, the system comprising: an aircraftbrake having a plurality of discs including an outer disc; an actuatorconfigured to apply a force to the outer disc to compress the pluralityof discs to reduce an angular velocity of wheels of the aircraft; acurrent sensor coupled to the actuator and configured to detect ameasured amount of current applied to the actuator; and a controllercoupled to the current sensor and configured to: determine an estimatedcurrent applied to the actuator based on the measured amount of currentdetected by the current sensor that is applied to the actuator,determine an adjusted current based on the measured amount of currentand the estimated current, and determine an estimate of the forceapplied to the outer disc based on the adjusted current.
 2. The systemof claim 1, wherein the controller is further configured to determinethe adjusted current using a PI controller to generate an output.
 3. Thesystem of claim 2, wherein the controller is further configured todetermine the adjusted current by performing low pass filtering on theoutput of the PI controller.
 4. The system of claim 1, wherein thecontroller is configured to determine the estimated current based on theestimate of the force.
 5. The system of claim 1, wherein the controlleris configured to determine a temporary estimated force based on theestimated current.
 6. The system of claim 5, wherein the controller isconfigured to determine a difference between the temporary estimatedforce and the estimate of the force.
 7. The system of claim 6, whereinthe controller is configured to determine a force difference bymultiplying the difference between the temporary estimated force and theestimate of the force by a constant value.
 8. The system of claim 7,wherein the controller is configured to determine the estimated currentby integrating the force difference.
 9. A method for determining a forceapplied to an outer disc of an aircraft brake by an actuator, the methodcomprising: receiving, at a controller of an aircraft and from a currentsensor of the aircraft, a measured amount of current; determining, bythe controller, an estimated current based on the measured amount ofcurrent; determining, by the controller, an adjusted current based onthe detected measured amount of current and the estimated current; anddetermining, by the controller, an estimate of the force applied to theouter disc based on the adjusted current.
 10. The method of claim 9,wherein determining the adjusted current is performed using a PIcontroller to generate an output.
 11. The method of claim 10, whereindetermining the adjusted current includes filtering, by a low passfilter, the output of the PI controller.
 12. The method of claim 9,wherein determining the estimated current includes determining theestimated current based on the estimate of the force.
 13. The method ofclaim 9, wherein determining the estimated current includes determininga temporary estimated force based on the estimated current.
 14. Themethod of claim 13, wherein determining the estimated current furtherincludes determining a difference between the temporary estimated forceand the estimate of the force.
 15. The method of claim 14, whereindetermining the estimated current further includes determining a forcedifference by multiplying the difference between the temporary estimatedforce and the estimate of the force by a constant value and determiningthe estimated current by integrating the force difference.